Effect of fine powder particles on quality of binder jetting parts

Despite their desired effects on quality metrics of powder metallurgy parts, fine powder materials are rarely used in powder-based additive manufacturing as powder feedstock materials due to their poor flowability and inefficient layer recoating. As such, process-structure-property relationships of powder-based AM processes have been explored primarily for coarse powder particle sizes (i.e., 25 μm–150 μm in diameter). With the new developments in powder recoating systems in modern binder jetting additive manufacturing (BJ-AM) printers, it seems now feasible to process fine powder materials that have average particle size of ∼10 μm (or smaller). In the current research, the use of fine copper powders (average particle size of 5 μm) in BJ process and its effects on green and final part properties are experimentally investigated. Specially, the authors studied the effects of different powder recoating settings on the density of printed green parts. The density of the sintered parts was also explored for various sintering parameters (i.e., heating rate and peak sintering temperature). Linear/volumetric shrinkage, microstructure and mechanical characteristics of sintered specimens were explored, and the results were compared to those of copper specimens made via coarse powder materials. The results indicated that fine copper powder resulted in parts with properties (UTS of 179.4 MPa and elongation of 42.2 %) greater than bimodal powder parts, which in turn eliminates extra time and work needed for powder mixing ratio optimization and blending process.